Mystery surrounds the death of a former butcher who opted for a life sleeping rough and gave away his possessions to those less fortunate, a coroner's court has heard.

While the body of Dubliner Fergal Kavanagh was found floating face down in the sea outside Ardglass harbour off the Co Down coast, his inquest was told the 54-year-old may actually have fallen into the water in his native city and drifted 80 miles northward.

Estimating that the homeless man may have been in the Irish Sea for more than a week before he was found by fishermen in August last year, a pathologist said it was impossible to determine an exact cause of death due to decomposition.

Dr Alastair Bentley, who told Belfast coroner's court that Mr Kavanagh had a degenerative coronary condition, suggested a number of possible scenarios.

"He may have had a heart attack and died and then fell into the water," he said.

"He may have had some heart event then fallen into the water and drowned, he may have entered the water and suffered a heart attack or he may have entered the water and drowned with no effect from the heart. So there are a number of possible reasons."

Noting there were no signs of injuries prior to death, the pathologist ruled out violence.

While the court heard evidence Mr Kavanagh had a drink problem, Mr Bentley said there was only a small volume of alcohol in his system when he died, which would have had very little impact on him.

Coroner Jim Kitson said the evidence required him to record the cause of death as undetermined.

"But my personal view is the most likely explanation is he had some cardiac event while walking along the sea shore of an evening and entered the water outside Dublin," he said.

Earlier, Mr Kavanagh's sister Mary Roche told the court of her shock when she heard her brother had been found dead in waters off Northern Ireland.

Mrs Roche, one of 11 children in the family, said her brother had no links to the region.

She said Mr Kavanagh opted to live on the streets, repeatedly turning down offers to stay with his siblings.

"He was homeless by choice," she said.

"I had always tried to get him to settle down, he would have had a bed in any of the families' houses. He was a lovely man, he was very generous.

"He dropped in and out of our lives when he wanted. I had no way of contacting him."

She added: "It was a life he chose for himself. All the children loved him."

Mrs Roche said when her brother was young and in work, before his life on the streets, he was always trying to help homeless people.

"When he was young he was a butcher and he used to bring home stuff and cook it and give it to homeless people," she said.

"He used to go into the city and feed the homeless."

With no leads or information as to who the dead man recovered from the water was, it took the Police Service of Northern Ireland (PSNI) two weeks to obtain a formal identification.

Having found no evidence of a link in Northern Ireland, officers passed a fingerprint to the Garda through Interpol.

That produced a match on gardai and prison records in the Republic of Ireland, as Mr Kavanagh had spent a period of time in custody in 2004.

PSNI constable Phil Quinn told the coroner that his inquiries ultimately led him to a Salvation Army hostel close to Dublin city centre.

Mr Kavanagh, who had been residing there for nearly a month, had been last seen there on August 4 last year. His body was found at Ardglass two weeks later on August 18.

Mr Quinn, who said Mr Kavanagh had been known to the Homeless Persons Unit (HPU) in Dublin since 2003, said he had withdrawn a benefit from the Post Office in Dublin at some point between August 2 and 7.

"He had a long history of sleeping rough in the Dublin 2 area," the officer added.

He said he rarely used homeless accommodation services, with only 28 recorded nights' stays in the 14 months prior to his death.

"His family gave him clothes, food and money but he refused to accept these," he said.

"Instead he chose to give all those things to homeless people he encountered."

Mr Quinn said Mr Kavanagh had appeared to be content in the hostel in the period before he died.

"He was living happily there," he said.

"There was no suggestion he had any difficulties or problems with any of the other service users."

Mrs Roche told the court that her brother loved walking along the canals in Dublin, sitting on the benches and reading poetry.

She said the family had spread his ashes at one of the benches.

Coastguard watch manager Judith McNeice used state-of-the-art tidal tracking technology to establish where the body may have entered the water. One of three locations the software identified was north Dublin, she told the court.

"It is not inconceivable that the person could have entered the water in the Dublin area and drifted to Ardglass," she said.

Passing his condolences to Mr Kavanagh's family members, Mr Kitson said it was a tragedy he was longer alive.

"He was a kind, generous hearted soul," he said.

"I have heard evidence he was inclined to give what meagre possessions he had to people he perceived less well off than himself."